1. Field of the Invention
The present invention relates to a golf club set.
2. Discussion of the Prior Art
Generally, the golf iron club set includes long iron clubs consisting of number two to four iron clubs, middle iron clubs consisting of number five to seven iron clubs, and short iron clubs consisting of number eight to ten iron clubs and a sand wedge.
In the head body of the iron club, a hosel portion and a face portion are integrally formed of metal such as soft iron and stainless steel. The lofts of the iron clubs increase with increase of the numbers indicative of the gradations of the iron clubs from the long iron clubs to the short ones. In the head body of this type, it is known that when the weight of the head body is distributed over the peripheral portion, a moment of inertia of the head body increases during the swing, to thereby achieve the directional stability of a ball.
Recently, there is a proposal of an iron club in which a recess is formed in the face portion of the metal head body, and a thin face plate made of a material that is lower in specific gravity than the head body, is fitted into the recess. There is another conventional iron club 7 as disclosed in Published Unexamined Japanese Patent Application No. Hei. 5-337222 or shown in FIG. 9. In the iron club, a through hole 4 is formed through a metal head body 1 to extend from a face portion 2 to a back portion 3, with its peripheral portion remaining, and a face plate 6 having a lower specific gravity than that of the head body 1 is fitted in a fitting recess 5 formed in the face portion 2.
In those conventional iron clubs, the face plate is lower in specific gravity than the head body, and therefore the weight of the head body is distributed over its peripheral portion. As a result, a moment of inertial of the head body increases during the swing, thereby achieving the directional stability of the ball.
In the iron club of the publication of Published Unexamined Japanese Patent Application No. Hei. 5-337222, the face plate 6 made of titanium or a titanium alloy is fitted into the fitting recess 5 of the head body 1 made of stainless steel or beryllium copper. Although titanium or a titanium alloy is lower in elastic modulus than soft iron or stainless, the face plate 6 must also serve as a vibration absorbing member for absorbing vibrations, developed when hitting the ball.
The manner to handle the iron club for hitting the ball is different with the numbers representative of iron clubs. The long iron club of the set is swung to hit hard a ball to secure a long flying distance. With increase of the club numbers from the long iron clubs to the middle iron clubs and the short iron clubs, the iron clubs are designed to increase the spin on the ball to more accurately land the ball at an aimed place.
Accordingly, a degree of the necessity of absorbing vibrations is also different with the club numbers. In the long iron club for hitting hard the ball, large vibrations are produced when hitting the ball. Thus, it is necessary to absorb the vibrations so as to prevent the vibrations from being transmitted to the elbows.
With increase of the club numbers of the used clubs to the middle iron clubs and the short iron clubs, the force to hit the ball becomes smaller and the degree of the necessity of absorbing the vibrations also becomes reduced. For those iron clubs, it is desirable that the absorption of the vibration is rather suppressed to leave some degree of the ball hitting feel, to thereby ease the control of the ball.
There has not been proposed yet a golf club set of the type in which the face plates of the iron clubs are different in thickness every club.
Therefore, particularly in the long iron club for hitting hard the ball, there is a possibility that vibrations generated in the iron club when hitting the ball is transmitted to the elbows, for example, in a state that it is unsatisfactorily absorbed. Further, it has been pointed out that the long iron club has a thick hitting face of the face portion, and hence a moment of inertia of the head body thereof is small, to thereby provide an unsatisfactory directional stability of the ball.
In addition, Published Examined Japanese Utility Model Application No. Hei. 3-19897 may disclose such a golf club set that a ball hitting face of the face portion becomes thinner as the club number increases from the long iron clubs to the middle iron clubs and the short iron clubs. However, the head body of each of those clubs is entirely made of the same metallic material.